A technique disclosed in co-pending U.S. patent application Ser. No. 419,705, filed on Sept. 20, 1982, now abandoned enables an optical designer to select compatible optical materials for the refractive elements of an optical system that is to be color-corrected at a specified number of wavelengths. A technique disclosed in co-pending U.S. Pat. application Ser. No. 260,106, filed on Oct. 20, 1988, enables the designer of a lens system that is to be color-corrected at a specified number of wavelengths to include one or more liquid lens elements among the lens elements of the system.
For optical systems used in certain applications, the cost of the optical materials used for the refractive elements is a major consideration. A so-called "disposable camera" is an example of an optical system for which the cost of the lens elements is of prime importance. A need has been recognized in the prior art for a lens system that is useful as a photographic objective or as a telescope objective, which is apochromatic and also well-corrected for monochromatic aberrations, and which comprises lens elements made of very inexpensive optical materials.